The Devil You Know
by Isisnofret
Summary: Selene Sinistra was not someone you would ever imagine fighting for the light, but when fate draws her into the war she has to decide which side she's really on. A decision made more difficult by the sudden involvement of Severus Snape in her life.
1. Default Chapter

The last few shafts of dying sunlight pierced the narrow, high windows of the small room, illuminating a large wooden table covered with mysterious looking bottles, jars and bundles of herbs. Shelves containing yet more exotic items obscured the walls of the room. Amid the usual ingredients one would expect to find in a potions laboratory, lace-fly wings, dragons blood, boomslang skin and many other similar items; there were other slightly more surprising objects. For instance, the equipment that looked suspiciously like muggle chemistry apparatus – a colourless gas was being condensed into a red liquid, and then evaporated again, of its own accord. Adjacent to this sat two small, ancient looking glass bottles, one of which contained a thick, deep red liquid, looking awfully like blood. The other was rather more remarkable, holding a dazzling fluid with the appearance of molten silver which was producing a light of it's own.  
  
In the light provided by both the bottle and the feeble rays of the fading sun, a dark haired woman was bent over the table, her focus on the ingredients she had been preparing for the last few hours. Her concentration was so great that she had not noticed the dwindling light, or the fact she had missed two meals while working on her task. Patiently she chopped, diced and shredded vast amounts of numerous ingredients, occasionally stopping to check the progress of a translucent blue potion bubbling in the cauldron beside her.  
  
Presently she heard a sound, which broke through her absorption, the sound of someone knocking on the front door of the manor she was currently inhabiting. Straightening up, she strained her ears to hear the conversation between the unknown visitor and Blinky, the house-elf. At such a distance the voices were just about identifiable, though she could not pick out any words. The high tones of the house-elf contrasted the deeper, yet still feminine tones of the caller. After a moment, a third voice joined the exchange, and, with a sigh of relief, the woman turned back to her work. If Blinky had decided to bother her mother with the guest then it wouldn't be something she had to handle herself. A good thing considering that she didn't want to leave the cauldron, which was simmering gently beside her.  
  
Therefore it was with a great deal of surprise she heard the unmistakable sound of footsteps approaching the room in which she was working. As she watched, the door crept open and Blinky edged inside.  
  
'Pardon miss, but you is having someone wanting to see you.' The house-elf looked around nervously. It was not often she was permitted in this part of the house.  
  
'Who is it? You know we don't allow anyone in here.' The woman glared down at the house-elf, wondering what had caused this unusual lack of obedience.  
  
'But I'm not just anyone' an oddly familiar voice purred from behind the door. With an uneasy feeling she stared at the door as it swung open slowly to reveal none other than the escaped Death Eater, Bellatrix Lestrange, her dark features framed by the frolicking candlelight from the hall.  
  
The silence was thick enough to cut with a knife as the two women scrutinized each other. Finally the quiet was broken by Blinky whimpering and scrambling out of the room. Bellatrix sent a disdainful look after the retreating house-elf, then snapped the door shut behind her.  
  
'What do you want?'  
  
'Is that any way to greet an old friend, Little Snake? Medusa was considerably more delighted to see me.'  
  
Bellatrix knew she was pushing it. There were very few people who could call Selene Sinistra by that particular nickname and remain able to tell the tale. However, she needed to know if she still had any power over the woman currently stood glaring at her. Another tense silence fell as the look on Selene's face changed from outright hostility to a cooler, calculating gaze. Bellatrix smiled to herself. Her Little Snake had never been good at masking her emotions. Quite unusual for a Slytherin really, she mused.  
  
'My mother always approved of our friendship. I do believe she would have preferred it if you'd been her daughter and not I.'  
  
Bellatrix smirked as Selene continued.  
  
'Excuse my abruptness. I was just extremely surprised to see you again. Of course you are always welcome here, Bella.'  
  
'Of course' Bellatrix agreed, still smirking. 'But I will admit to this being more than just a social call. There is something I want from you.'  
  
'And what is that?' Selene enquired cautiously, distracted for a moment by the hissing of the potion she was in the middle of brewing.  
  
'A great honour, Little Snake.' Bellatrix spoke as she watched Selene add a handful of some indefinite substance to the cauldron. She was not offended, being well aware that Selene was concentrating on her words just as much, if not more, than on the potion.  
  
'Through me, you have come to the attention of the Dark Lord himself.' Watching closely, she saw Selene stiffen slightly, faltering a little in her stirring of the potion, which had now turned a intense red.  
  
'He is pleased by what he has learned of you, and is willing to allow you to enter into his service.'  
  
'Into his service? Exactly what do you mean?' Selene asked sharply, looking Bellatrix in the eye, her potion forgotten. Its red glow illuminated her face, casting her features into sharp relief.  
  
'I mean that you may finally become one of us; at long last, a Death Eater. Given that you pass our little loyalty test of course. You must prove yourself both useful and worthy before the Dark Lord will accept you into the fold, but I'm sure you expected that...'  
  
This was the moment of truth. Bellatrix watched Selene closely for any sign of what she was thinking, not that that was difficult with Selene displaying her feelings like an open book. Her wand lay on the table, mere centimeters from her hand. If she decided to fight, Bellatrix knew she had to be ready. Few managed to defeat Selene Sinistra in a duel without coming away with major injuries themselves. Not since her early school days, anyway.  
  
Fortunately Bellatrix had little to worry about. The thought of refusing had only briefly flown through Selene's mind. To refuse an offer as direct as that would be a death sentence. If she did manage to fight off Bellatrix, something she could not be sure of doing, her beloved potions lab would be ruined. And for nothing. There would be no way she could run from the Dark Lord's followers forever. But to join the inner circle... Well, she could be very useful to Albus Dumbledore.  
  
Selene Sinistra was not someone you would ever imagine fighting for the light, at least not if you knew her well. Her interests tended towards the dark side, demonstrated by her willingness to brew and test illegal potions on live subjects. Under Voldemort she would have no problems continuing with her research, unhampered by the need for secrecy. Unfortunately there was one thing Selene Sinistra despised – to be controlled or owe absolute allegiance to another being. Which happened to be the one thing Lord Voldemort demanded from all his followers.  
  
These thoughts streaked through Selene's mind, concealed from Bellatrix's watchful eye. Selene allowed her face to register shock, slowly replaced by a growing, satisfied, smirk. She grinned inwardly at her fellow Slytherin's arrogance. Just because Bella had been able to read her every thought while they were at school didn't mean she still could. A lot had happened to Selene in the time since then. Enough for her to master the art of masking her feelings for one.  
  
'Just tell me what I am required to do. I'm sure I will not disappoint.'  
  
'It is for the Dark Lord to decide whether you disappoint him. You will make no assumptions.' Bellatrix snarled. She waited until Selene looked sufficiently contrite, before continuing. 'He has a very special task for you. One that you alone are ideally positioned to carry out. How close are you to Severus Snape?'  
  
'Severus? Well... we work together. He is the head of house, and I am the junior professor.' Selene raised an eyebrow at the route the conversation was taking.  
  
'Are you friends?'  
  
'We're... acquaintances. I don't think Severus has anyone he'd really call a friend. I mean, we're on first name terms, and we occasionally share a bottle of wine after a house meeting. But other than that we don't spend time together when not to do with official Hogwarts business.'  
  
'Well I suggest you start. I take it you are aware of Severus's past allegiances?'  
  
'He was accused of being a Death Eater, if that's what you mean.' Selene answered carefully, a little unsure of where the exchange was heading.  
  
'He was a Death Eater. A most useful one too. A little before the events with the Potter child, he managed to convince Dumbledore of his change of heart, and desire to help the old fool by becoming a spy for him. It was that which kept him out of Azkaban while the rest of us suffered.' Bellatrix paused to glower at the thought of the cowards who escaped, and Selene took the opportunity to interrupt.  
  
'He was spying on you for Dumbledore?' She asked, surprised. 'So I take it you want me to teach him that no one betrays the Dark Lord and gets away with it?' A predatory grin lit her face at the thought. 'I have a new poison I've developed that I'm dying to test on a human subject...'  
  
'Listen to me, Little Snake. I admire your enthusiasm, but wait for your instructions! We don't want you doing something that might displease the Dark Lord now, do we? Severus gained Dumbledore's confidence, allowing him to spy on the trusting fool, for us. A very useful position to have a Death Eater in, as I'm sure you will agree. Severus is continuing in that capacity as we speak, trying to find the location of the Order headquarters.  
  
'Unfortunately, he appears to be having little success. The Dark Lord is getting suspicious. Is this lack of information purposeful? Perhaps Severus is not as loyal as we previously thought. Normally anyone suspected of being a traitor would be dispensed with immediately, but Severus is too useful. You are to scrutinize his every movement. Do whatever you must, but find out where his loyalties lie.'  
  
Selene frowned, trying to take in the large amount of information that had been thrown at her. Severus Snape, a spy? She knew about his sinister past of course, but not of his current actions. Whose side was he really on? She realised she knew the man far less well than she originally thought. This was going to be an interesting assignment.  
  
'How am I to find this out?' she asked, not really expecting an answer. Still it was better to let Bellatrix think she needed her help. She'd seem less of a threat that way.  
  
'That's for you to work out. Demonstrate to the Dark Lord that you actually have a use! We already have enough mindless followers, we need Death Eaters who can sort out problems by themselves.'  
  
Selene nodded, her mind already on the problem. The cauldron hissing again drew her attention and she quickly added the next series of ingredients, while Bellatrix swept the room with her eyes. Noticing the bottle of silver fluid she sauntered over and examined it closely. Reaching out a hand to pluck the bottle from the shelf, she stopped abruptly when she felt Selene seize her arm. Looking at the younger woman, who had a small smile playing at the corners of her mouth, she raised an eyebrow.  
  
'Please don't touch that. It's rather rare, and it would be... problematic replacing it if you accidentally spilled it.' Selene remonstrated, releasing Bellatrix's arm.  
  
Bellatrix snorted with amusement, and turned to look at the bottle once more.  
  
'You always were protective of you potion supplies. What is this anyway?' she asked lazily. 'It's pretty.'  
  
'Unicorn blood' Selene smirked at the look of surprise on Bellatrix's face.  
  
'How on earth did you get hold of that? Surely you didn't collect it yourself...'  
  
'Of course not.' Selene laughed. 'What do you take me for? And do you really expect me to reveal my sources? Let's just say I can be very persuasive.' She shared a conspiratorial grin with Bellatrix, who moved towards the door.  
  
'I suggest you utilize that persuasive nature of yours in your task. I'm sure you'll have your work cut out for you with Severus.' With a final smirk, she disappeared through the door, leaving Selene gazing thoughtfully at the floor. 


	2. Chapter 2

The staff meeting that took place the day before the beginning of term was always a rather stressful time for most of those involved. So many last minute preparations needed to be made in advance of the hundreds of children that would be arriving the next evening. Professors hurried around finishing class schedules, talking anxiously to one another, or just sat concentrating on the tasks they had yet to complete. Severus Snape, however, sat calmly on a sofa in the corner, coolly surveying the activity before him with a look of detached amusement. He always finished his preparations well ahead of time, and actually took pleasure in watching the other teachers' anxiety.  
  
Over in the corner he could see an exceptionally thin-lipped Minerva McGonagall deep in conversation with the latest Defence Against the Dark Arts professor, Professor Dexter. He had been introduced to Dexter half an hour ago, and already he did not like the man, although that may have been due to the fact that Dexter had got the job he was still after, Snape admitted to himself. Glancing around the room he saw the door open, and Selene Sinistra slip inside. She made her way partly into the room before stopping and turning to sneer at Hagrid, who had just knocked Flitwick into the table of tea and biscuits with an over enthusiastic back slap. Her long oily black hair hung limply about her face as she watched Hagrid apologizing to the diminutive professor, blending with her plain black and slightly oversized robes that hung shapelessly over her slim frame. As if aware of his scrutiny, she suddenly turned to look at him, her blue eyes meeting his black ones. She seemed about to approach him when a call from Minerva caught her attention.  
  
'Professor Sinistra' Snape smirked at the way Minerva's lips got even thinner (he had not thought it possible) as Selene sauntered over. It was no secret that the two women disliked each other. Minerva never addressed Selene by her first name, though she did with all the other professors, and Selene never failed to sneer if the deputy headmistress came within eyesight.  
  
'I would like to introduce you to Darius Dexter, the new Defence Against the Dark Arts professor. Darius, this is Selene Sinistra, Astronomy professor.'  
  
'Charmed, I'm sure' Selene drawled. Dexter grasped her proffered hand, and mumbled a reply that Snape didn't catch. The new professor's eyes passed over her face briefly before focusing again on Minerva. Snape frowned. It was something he had seen often when people spoke to Selene, almost as if her presence barely registered.  
  
'If you'll excuse me...' Selene quickly extracted herself from the conversation with a wan smile, sliding into the sparse crowd of teachers and somehow out of sight.  
  
'Ah. Severus. I see you're already organized for the coming year.' Albus' voice interrupted his contemplation of his junior professor. Snape simply inclined his head, not wishing to be drawn into conversation.  
  
'Doesn't the thought of a new school year, all those new students eager to learn, fill you with enthusiasm?' Dumbledore enquired, his eyes twinkling cheerfully.  
  
'The year I come across a class of students eager to learn, I'm sure I will discover my long lost enthusiasm.' Snape allowed his voice to veritably drip sarcasm, in another attempt to put an end to the dialogue. He found his eyes roaming the room, searching for Selene, though he could not say why he was looking for her. 'Until that day, however, please excuse my pointed lack of fervor over teaching a school of Dunderheads.'  
  
'Albus?' Minerva's request spared Snape from any further banter. The headmaster clapped him on the back, jovially, before turning to his deputy.  
  
Scanning the group of professors again, Snape glowered. How could she disappear in such a small crowd?  
  
'I believe I'm the one you're looking for?' a voice breathed in his ear. Starting, he whipped round, to find himself face to face with Selene. She had her elbows propped on the back of his seat, chin resting on her hands as she gazed down at him, a small smile playing about her lips.  
  
'Yes, I was.' He recovered himself quickly, searching for, and finding, a reason he would have to seek her out. 'We need to arrange a Slytherin staff meeting.'  
  
Standing up, she stretched then nodded, slipping round the sofa and onto the seat beside him. 'When do you propose we schedule it? Tonight?'  
  
'No, it would be more useful to hold it Monday evening, after the first full day.'  
  
'Well, it'll have to be late then. I have classes until 1.30 in the morning.' She yawned, and stretched her arms out again. 'Sometimes I wish I had a normal teaching schedule. I don't understand why Albus constantly arranges it so that I have midnight practical classes followed by 9 o'clock theory lessons the next morning.'  
  
'He does seem to enjoy torturing us' Snape conceded, with a slight smirk. 'However, term hasn't started yet, so that's obviously not the reason you're so tired today.'  
  
'No, it's a potion I've been working on. It took 36 hours to brew and required almost constant attention. And now all the anti-drowsiness potions I took are starting to catch up on me.' She yawned again, allowing her head to drop back and her eyes drift shut.  
  
'A potion? I haven't seen you in the lab.' Snape frowned. True, he hadn't been in his laboratory much in the past couple of days, but surely he would have seen her if she'd spent that amount of time there. Then another thought struck him. Narrowing his eyes, he inquired, 'And what exactly were you making?'  
  
'I didn't want to disturb you. So I used the room of requirement, like I usually do.' She opened her eyes to find him still eyeing her carefully. 'Oh relax, it wasn't anything illegal. I know better than to do that right under Albus' nose.' At that he let out a snort of humorless laughter.  
  
'We both know that's untrue, so don't waste your breath. I repeat, what exactly did you brew?'  
  
She observed him quietly for a moment, before smiling ruefully. 'Nothing gets past you does it?' He raised an eyebrow, and she sighed. 'If you must know, it's something I developed myself - a variation on the Imperious potion.'  
  
'What?!' he hissed, causing several heads to turn in their direction.  
  
'Severus, don't make a scene' she replied composedly. 'I only want a few more house responsibilities. It's not like I told you Harry Potter was your son!' At this the few who had turned to see what was going on laughed and went back to their previous activities. Lowering her voice she continued. 'You're head of Slytherin house. You're supposed to be able to be subtle!' He opened his mouth to make a scathing reply, but, raising her hand in a placating gesture, she cut him off. 'Don't worry. I've made just enough alterations to make it legal. For a start, I've replaced the human blood with that of a pig, and the basilisk's eye with simple boomslang skin.'  
  
'You used boomslang skin to replace basilisks' eyes? How in Merlin's name did you manage that?'  
  
'You're supposed to be the Potions Master.' she smirked. Seeing that he wasn't amused, she continued wearily. 'I added vast amounts of beetles eyes.'  
  
Comprehension dawning, he nodded. 'That's why it took a day and a half. You had to add them one by one to make sure they didn't react violently with the wolfsbane I assume you used?' She nodded. 'Well, that takes care of the illegal ingredients, but potions which mirror the effect of the Imperious curse are themselves banned.'  
  
'Ah, that's the beauty of it. The slow fusion of the pig's blood, beetles' eyes and powdered dragon scales make this potion impossible to detect in the body. The addition of a hair from the head of the potion brewer means only she can control anyone who imbibes the substance. So it's also impossible for anyone else to prove what the potion does, making it safe to leave lying around a lab. Genius, isn't it?' she finished with a triumphal grin.  
  
'Indeed. If it actually works. And that is something which I am highly skeptical about.' He smirked at the look of indignation on Selene's face. 'You want me to believe that you have succeeded in creating something non of the greatest dark wizards have ever come close to achieving?'  
  
Narrowing her eyes at him, she let out a derisive snort. 'I know what you're doing. You're trying to goad me into taking you to the lab and showing you how I did it.' She sighed. 'Do you really believe I'm so stupid?' There was a pointed silence, in which he merely raised an eyebrow. In response, Selene smiled slightly. 'You know, I might be persuaded... If you do something in return for me.'  
  
'Why do I get the feeling that your request will be unacceptable?' he inquired.  
  
'Because you never find anything acceptable? All I want is for you to work with me from time to time.' She leaned in towards him, her lips inches from his ear. 'There are certain things I want to try that require more than one person, and it's not like I could ask just anyone.' Veritably purring, she continued on. 'I need someone who is good, and who is willing to overlook certain... slightly lees than legal aspects of the work. Just imagine what we could do together...'  
  
'Loose our jobs, perhaps?' he asked, acerbically.  
  
Leaning back and fixing him with an intense gaze, she smiled wryly, 'Unlikely. Dumbledore seems to have a particular fondness for you.'  
  
He remained silent for a moment, an inscrutable expression on his face. Deciding not to push it, Selene shrugged and broke eye contact. 'Look, it was just an idea. It doesn't matter.'  
  
They lapsed into silence for a few minutes, Snape once again surveying the room indifferently. Selene, however, was not so patient. After the fifth stolen glance she decided to try again.  
  
'You'd be able to keep an eye on me.' She blurted out.  
  
He turned his head and looked her up and down, an amused expression on his face. 'And why on earth would I want to do that?  
  
Giving him a mock-offended glare, she retorted, 'So I don't do something stupid and loose my job? You'd never get another junior professor as good as me, you know!' When he didn't look sufficiently impressed, she added 'Are you really going to give up the chance of spending countless evenings all alone with a beautiful woman?'  
  
Snape snorted. 'Beautiful woman? You really think a lot of yourself. I don't see crowds of mean queuing up to have a date with you.'  
  
'That's because you don't see me at weekends' she laughed. 'Come on, you can't deny I have beautiful eyes. Like chipped ice, or so I've been told.'  
  
Their eyes locked, and he had to admit to himself that she was right, her eyes were remarkable. Not that the rest of her was that amazing. But she'd amused him, and that was not something that happened very often.  
  
'Ok'  
  
'So I am irresistible after all?' Selene replied after a brief stunned silence, surprised by his sudden change of heart. She hadn't seriously expected that to work, in fact she'd cringed inside when she'd said it.  
  
'Hardly. However, I would like to know how you brewed that potion.' At her smug grin he added, 'And see if it works of course.'  
  
'Of course' she laughed 'When do you want to do it?'  
  
'I don't know. We'll discuss it on Monday. Excuse me.' With that he stood and crossed the room to where Professor Sprout was studying her first year class list. Selene followed him with her eyes, satisfied that the first stage of her plan had worked satisfactorily. 


End file.
